850 cylinder configurations

Norton46 · May 22, 2017

Hi
While in a discussion about Nortons, a friend is planning to use a cylinder which has a bore of 77mm, however it has a base flange for the waisted stubs like a 750. It does not have the 4 cap screw mounting bolt holes.
I have never seen or heard of such a thing and am waiting on photos.

Has anyone else heard of such a configuration?

Thanks

Mark

comnoz · May 22, 2017

Norton46 said:
Hi
While in a discussion about Nortons, a friend is planning to use a cylinder which has a bore of 77mm, however it has a base flange for the waisted stubs like a 750. It does not have the 4 cap screw mounting bolt holes.
I have never seen or heard of such a thing and am waiting on photos.

Has anyone else heard of such a configuration?

Thanks

Mark

No,
and considering that there is minimal material between the base nut relief and a 73mm bore -they were known for cracking if they were bored larger than 74mm.

With a 77mm bore the pistons would be visible behind the base flange nuts.... :shock:

lcrken · May 23, 2017

Never heard of anything like that. Please do post pictures when available. Ask your friend to measure the bore again. Like comnoz said, no way to bore 750 cylinders to 77 mm.

Ken

Dances with Shrapnel · May 23, 2017

comnoz said:
With a 77mm bore the pistons would be visible behind the base flange nuts.... :shock:

Would that be a bad thing?

Rohan · May 23, 2017

lcrken said:
Never heard of anything like that. Please do post pictures when available. Ask your friend to measure the bore again. Like comnoz said, no way to bore 750 cylinders to 77 mm.

Measure again, good advice.

Being +0.160 oversize (!!) is not going to stop an 'enthusiastic' owner, shall we say,
I've heard of dommie cylinders out so far you could see the piston between the fins. !
It was joked the fins went up and down with the pistons....

comnoz · May 23, 2017

Dances with Shrapnel said:
comnoz said:

With a 77mm bore the pistons would be visible behind the base flange nuts.... :shock:

Click to expand...

Would that be a bad thing?

Naw, no big deal. Just a little oil on your boots...

I bored an 850 cylinder once and fitted 920 pistons with no sleeve. It lasted almost 900 miles before it developed and oil leak. If you looked behind one of the front head stud nuts you could see the piston going up and down where the paper thin piece of cast had departed...

mdt-son · May 25, 2017

Norton46 said:
Hi
While in a discussion about Nortons, a friend is planning to use a cylinder which has a bore of 77mm, however it has a base flange for the waisted stubs like a 750. It does not have the 4 cap screw mounting bolt holes. I have never seen or heard of such a thing and am waiting on photos.

Hi Mark,
I guess your friend has a sleeved 750 cylinder. I bought a barrel on FleeBay assumed to be for an 850 and had it relined by L.A.Sleeve using 77mm (850) sleeves. Turned out the barrel was for a 750 motor. The liner works but spigots are awfully thin and the liners are visible between fins. I've not fitted the barrel as yet. The possibility of a cracking base is a worry.

Cheers, Knut

850 cylinder configurations

Norton46

comnoz

lcrken

Dances with Shrapnel

Rohan

comnoz

mdt-son

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